Add little endian import to Bignum
The function `mbedtls_mpi_read_binary()` expects big endian byte order,
but we need to be able to read from little endian in some caseses. (For
example when handling keys corresponding to Montgomery curves.)
Used `echo xx | tac -rs .. | tr [a-z] [A-Z]` to transform the test data
to little endian and `echo "ibase=16;xx" | bc` to convert to decimal.
diff --git a/library/bignum.c b/library/bignum.c
index 87015af..d28d3be 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -814,6 +814,34 @@
}
/*
+ * Import X from unsigned binary data, little endian
+ */
+int mbedtls_mpi_read_binary_le( mbedtls_mpi *X,
+ const unsigned char *buf, size_t buflen )
+{
+ int ret;
+ size_t i;
+ size_t const limbs = CHARS_TO_LIMBS( buflen );
+
+ /* Ensure that target MPI has exactly the necessary number of limbs */
+ if( X->n != limbs )
+ {
+ mbedtls_mpi_free( X );
+ mbedtls_mpi_init( X );
+ MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, limbs ) );
+ }
+
+ MBEDTLS_MPI_CHK( mbedtls_mpi_lset( X, 0 ) );
+
+ for( i = 0; i < buflen; i++ )
+ X->p[i / ciL] |= ((mbedtls_mpi_uint) buf[i]) << ((i % ciL) << 3);
+
+cleanup:
+
+ return( ret );
+}
+
+/*
* Import X from unsigned binary data, big endian
*/
int mbedtls_mpi_read_binary( mbedtls_mpi *X, const unsigned char *buf, size_t buflen )